Surface mount PRTs

Citation

(2003), "Surface mount PRTs", Sensor Review, Vol. 23 No. 3. https://doi.org/10.1108/sr.2003.08723cad.005

Surface mount PRTs

Surface mount PRTs

Keywords: Surface mount technology, Miniaturization

Miniaturization and low power are the elementary features dictated by development engineers for the state-of-the-art electronic systems. With two world innovations in the area of platinum temperature sensors, Heraeus Sensor-Nite has made a decisive step towards these two goals. The SMD 603 (surface-mounted device) with its dimensions of 1.6 × 0.8 mm has only half the size of its predecessor, and the new SMD 805 is the first platinum sensor of this type to feature a nominal resistance of 10 k (Plate 5). The result is that, on the one hand, higher packing densities on electronic PCBs are achieved or, on the other hand, it is possible to benefit from the full range of advantages of platinum temperature sensors in the case of the 10 variant. This particularly refers to the extremely high measuring accuracy and longterm stability.

Plate 5 The SMD 603 and the SMD 805

Optimizations of carrier substrate and photolithographic production process

Successful optimisations of the photolithographic production process and the carrier substrate are the basis for the venture into new dimensions. The extremely fine platinum microstructures require and absolutely planar surface, which is not offered by traditional carrier materials. Conductors in meandering structures with a spacing of 6μm at the best have so far been the state-of-the-art technology for platinum temperature sensors. Thanks to Heraeus Sensor-Nite, this value has now been surpassed three times. In both innovations, platinum meander widths and spacings as small as 2-3μm are achieved. The SMD 603 utilizes this innovative step for further miniaturization, whereas in the 10 k SMD, a higher, optimised nominal resistance is reached.

The platinum SMD 603 miniaturization and price advantage

For the users of platinum temperature sensors, miniaturization of the SMD the users of platinum temperature sensors, miniaturization of the SMD 603 does not only represent a benefit regarding higher packing densities. Moreover, it is the basis for a substantial price advantage. As a result of the considerably smaller dimensions, clearly higher yields can be accomplished with a standard 2×2 in. substrate of the 603 series. In combination with numerous process optimisation, which have significantly reduced the production costs in the recent past, pricing is likewise influenced. According to Dr Karlheinz Wienand, R&D Director at Heraeus Sensor-Nite, the prices of this new SMD 603 sensors are in the range of technically comparable thermistors.

The Pt SMD in 10 k – benefit from all advantages of platinum sensors

For the evaluation of signals from Pt temperature sensors, voltage divider circuits, operated at 5 V, are normally used. In the ideal case, series resistor and measuring resistor are identical so that an optimum nominal resistance of 8-12 kΩ is achieved. The power loss or the self-heating effect of the sensors is, hence, so small that it can be neglected. The temperature accuracy reaches tolerance values lower than 0.15 per cent. As a result, the known benefits of platinum temperature sensors can be utilized in their full range:

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  extraordinarily high precision (<0.15 per cent),

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  virtually linear characteristic,

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  very broad temperature range ( 196°C-1.000°C),

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  low drift,

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  extreme longterm stability and reliability, and

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  easy reproducibility.

For further information, please contact: Mr John Collier, Heraeus Sensor-Nite (UK), 655 Sheffield Road, GB-Reading, RG1 8PP, Great Britain. Tel: 0044/1246454849; Fax: 0044/1246453898; E-mail: john.collier@sensor-nite.com